Existentially closed groups are, informally, groups that contain solutions to every consistent finite system of equations and inequations. They were introduced in 1951 in an algebraic context and subsequent research elucidated deep connections with group theory and computability theory. We continue this investigation, with particular emphasis on illuminating the relationship with computability theory.

In particular, we show that there are existentially closed groups computable in the halting problem, and that this is optimal. Moreover, using the work of Martin Ziegler in computable group theory, we show that the previous result relativises in the enumeration degrees. We then tease apart the complexity contributed by “global” and “local” structure, showing that the complexity of finitely generated subgroups of existentially closed groups is captured by the PA degrees. Finally, we investigate the computability-theoretic complexity of omitting the non-principal quantifier-free types from a list of types, from which we obtain an upper bound on the complexity of building two existentially closed groups that are “as different as possible”.

This article proposes that theoretical debates over the Rule of Law can be revitalised through careful focus on methodology. First, it contends that the prevalent methodology of theory-construction is a rationally reconstructive form of conceptual analysis which makes deadlock practically inescapable. The methodology requires the invocation of deeply controversial conceptual cross-references: to reconstruct vague intuitions about the Rule of Law, theories are compelled to invoke other concepts over which deeply engrained disagreements persist. Second, turning to the possibility of overcoming or mitigating deadlock through critical argument, it argues that the capacity of critique to pose meaningful challenges to rival theories turns on its treatment of its target’s conceptual cross-references. Dissonant critique, which is premised on the rejection of a rival theory’s defensible conceptual cross-references, is seldom productive. Internal critique, which proceeds from rival theories’ conceptual cross-references, poses more meaningful challenges and is more philosophically productive.

Death elicits needs such as an adequate farewell. Attending and responding to such needs is central to the organization of death, that is, the management of end-of-life situations before, during, and after a person’s passing. However, prior research points to insensitivity and marginalization of such needs in the organization of death. I refer to this phenomenon as “organized carelessness,” and I draw on the ethics of care to examine how it is produced. Based on a case study in the field of funeral services, I show how organized carelessness emerges through four processes: sequestration, deauthorization, reskilling, and moralization. Together, these processes contribute to stripping away ethical choices in relationships with the bereaved, and moving forward with little, if any, sensitivity and responses to their specific needs for an adequate farewell. These findings have implications for understanding carelessness in the organization of death in particular, and in organizational life more generally.

The unique reproductive strategies of botryllid ascidians, which include both asexual and sexual mechanisms as well as an extensive capacity for regeneration, contribute to their fast population growth and wide-ranging ecological effects. These colonial organisms have unique ecological adaptations and responses to environmental factors, yet comprehensive comparative studies on their environmental preferences remain scarce. We conducted an experimental study to explore the asexual reproduction and regeneration response of Botrylloides niger and Botryllus humilis colonies to varying salinity (36.5–39.5 PSU) and temperature (26 ± 1–30 ± 1°C) levels. Experimental findings highlighted species-specific preferences and stress responses: B. niger demonstrated higher tolerance to elevated salinity (39.5 PSU) with optimal growth rates at 26 ± 1–30 ± 1°C, whereas B. humilis displayed a preference for lower salinity and tendencies towards vascular budding at higher temperatures (30 ± 1°C). These observations suggest potential niche differentiation and ecological success, particularly in Mediterranean conditions, implying possible coexistence without intense competition in similar habitats. This research offers insights into the adaptive mechanisms of these ascidians, shedding light on their ecological roles and potential implications in coastal ecosystems amid changing environmental scenarios.

Current models of scientific inquiry assume that scientists all share the same evaluative standards. However, scientists often rely on different yet legitimate ones, a feature we call evaluative diversity. We investigate how scientific success is affected by diversity in evaluative standards through computer-based simulations. Our results show that communities with diverse standards benefit substantially from scientists sharing all the approaches they explored, regardless of whether they considered them valuable. Moreover, we find that even a moderate degree of evaluative diversity can, under certain conditions, lead scientists to reach more satisfying results than those they would reach in homogeneous communities.

From the shores of the Black Sea to the banks of the Mississippi River, more than mere distance separated the nineteenth-century port cities of Odessa and New Orleans. Although these ports emerged in distinct political and geographical settings, a comparative analysis reveals striking parallels between these two southern metropolises, each positioned at the territorial edge of continental empires. This article aims to examine the common challenges these cities encountered in their development, the factors that divided their cosmopolitan populations and how socio-environmental vulnerabilities contributed to their urban fragmentation.

Using wearable sensors to evaluate workers’ performance is challenging with existing sensor techniques. It requires detecting not only limb motions but also the onset and offset of specific actions. Commonly used inertial measurement units (IMUs) can be combined with surface electromyography (sEMG) to detect muscular activity. However, sEMG requires skin preparation and careful sensor placement, and can be affected by sweat or motion artifacts. To address these limitations, we used a wearable system combining IMUs and force-sensing resistors (FSRs), where IMUs capture joint kinematics and FSRs detect grasping actions. The system included three IMUs (on the trunk, upper arm, and forearm) and two FSR arrays (on the upper and lower arms). The system was first validated in a laboratory setting against an optical motion capture system with 10 healthy young adults performing isolated upper limb movements and mimicking lifting tasks. The results showed high agreement in joint angle estimation (coefficient of multiple correlation = 0.95 $ \pm $ 0.04), with a maximum root mean square error of 8.7 $ \pm $ 2.92°, and a mean absolute timing error for grasp detection of −0.59 seconds. To evaluate its applicability in real-world scenarios, a pilot in-field test was then conducted with two manufacturing workers (using and not using a passive shoulder exoskeleton) during a repetitive panel-packing task. The test shows highly consistent grasping detection, which allowed segmenting the task with a small variability in task duration (maximum coefficient of variation = 5.16$ \% $). These findings demonstrate the feasibility of using the proposed method in industrial environments to analyze upper limb motion and grasping activity.

Examining the early post-colonial Beirut International Airport (BEY), we make two arguments. First, BEY had the potential to become the Middle East’s largest airport only because from the mid-1800s Beirut, which had a large maritime port, had been the Arab East’s global cultural, commercial, communications and transport hub, which created a path dependency. Second, BEY deepened Beirut’s regional-global role throughout the 1960s, making it an aero-city piggybacking on a port-city. We explore four dimensions. First, in urban planning, the government was exceptionally interventionist where BEY was concerned; second, BEY’s construction triggered sociopolitical conflicts; third, BEY intersected with Palestinian and Lebanese unskilled labour flows; and, finally, air-travel, including tourism, affected Beirut’s cityscape deeply yet unevenly.

The upcoming Square Kilometre Array Low Frequency (SKA-Low) interferometer will have the required sensitivity to detect the 21 cm line from neutral hydrogen during the Epoch of Reionisation (EoR). In preparation, we investigated the suitability of different fields for EoR science with the 21 cm line, using existing observations of candidate fields from the Murchison Widefield Array (MWA). Various image and calibration metrics were extracted from archival MWA observations centred on $z \sim 6.8$. We explore the usefulness of these metrics and compare their behaviour between different fields of interest. In addition, a theoretical approach to quantifying the impact of different fields on the power spectrum is also provided. Gain uncertainties were calculated based on the positions of the calibrators within the beam. These uncertainties were then propagated into visibilities to produce cylindrical power spectra for various fields. Using these metrics in combination with the power spectra, we confirm that EoR0 ($\text{R.A.} = 0\,\mathrm{deg}$, $\text{Dec} = {-}27.0\,\mathrm{deg}$) is an ideal EoR field and discuss the interesting behaviour of other fields.

Nineteenth-century Calcutta was a premium port city and the nerve-centre of the British Empire’s commercial activities in South Asia. In many ways it was presented as a promising mercantile global metropolis – a symbol of efficiency, infrastructure and urban modernization – celebrated in contemporary colonial accounts and literature.1 However, looking beyond, it is possible to locate other perspectives that challenge the colonial narrative. Reading both against the grain of colonial archives and closely examining Indian accounts, this article highlights the gaps in its smooth functioning, and uncovers local practices that challenged metropolitan blueprints. As seen here, it was possible for the everyday city to pose a serious challenge to European – purportedly universal, and therefore global – models of urbanization implemented by the colonial government. Calcutta here emerges as much a product of its own social, cultural and natural environment, as that of global modernization regimes unleashed by colonialism, the legacy of which can be seen even today.